Devices of this type are used, for example, for clamping together two tubes disposed end-to-end.
Said tightening system is most often a nut-and-bolt fastener.
In addition, most often, the belt is of annular general shape centered on an axis referenced A, and the collar is tightened by reducing the diameter of the belt. Thus, in the present patent application, the axial direction corresponds to the direction of the axis A, and a radial direction is a direction perpendicular to the axis A. The circumferential direction is defined relative to the circumference of the belt.
U.S. Pat. No. 848,139 and Patent Application EP 0 367 169 A1 describe known examples of clamping devices of the above-mentioned type.
Such known devices comprise collar belts of generally annular shape and nut-and-bolt fasteners serving as the tightening systems. The tightening walls and the connection portions of the lugs of the collar are provided with openings through which the shank of the bolt passes. Assembly clearance exists between the openings and the shank of the bolt. During tightening, the head of the bolt and the nut come to bear against respective ones of the tightening walls of the facing lugs, so as to bring the lugs closer together and so as to cause the collar to be tightened, by reducing the diameter of the belt.
Although the collar of U.S. Pat. No. 848,139 is generally satisfactory, it has been observed that, for certain demanding uses, each lug is deformed (it “unfolds”) under the effect of the tightening forces (the amplitude of that deformation depending on the above-mentioned assembly clearance) at the hinge zone between the connection portion and the belt of the collar. The facing lugs then tilt towards each other, thereby reducing the effectiveness of the clamping of the collar.
That problem of the lugs tilting is avoided with the collar of EP 0 367 169 A1 because the tightening walls of the lugs are welded to the belt of the collar. However, welding the tightening walls to the belt constitutes an additional and costly step in manufacturing the collar. In addition, the link formed by such welding is, by nature, a totally rigid link that deprives the tightening wall of any freedom of movement. However, the tightening wall constitutes the bearing zone for the bolt head or for the nut, so that it is generally preferred for said wall to continue to have a small amount of freedom of movement so that the bolt head or the nut bears optimally against said wall (naturally, that freedom must remain limited in order not to reduce the effectiveness of the collar).